The research design includes interviews with persons from a suburban area involved in a heroin epidemic. Interviews were conducted with four groups of persons: 1) persons who became addicted to heroin, 2) persons who experimented with heroin but did not become addicted, 3) persons who were exposed but did not try heroin, and 4) a randomly selected comparison group from the same population. All persons involved in the study came from one of two adjacent high schools. The study population is primarily White with some persons of Mexican-American background. The primary research objectives pursued in this investigation are listed below: 1. To describe the pattern of diffusion of a heroin epidemic. The main goal will be to evaluate the applicability of the contagious disease model as an explanation and description of the spread of heroin use. 2. To investigate the social and psychological determinants of levels of heroin use. The basic independent variables examined will be the nature of the involvement of the individual in family and school, peer group relationships, and selected personality characteristics. We are interested in how these independent variables can be used to distinguish between the four groups listed above.